The present invention relates generally to a GPS signal receiving apparatus that receives signals from GPS (Global Positioning System) satellites to measure the position and speed of a signal receiving apparatus and, more particularly, to a GPS signal receiving apparatus that is capable of being held by or attached to a human arm to measure the user's position during running or walking, as well as the user's moving speed and moving distance.
Conventionally, the GPS system has 24 GPS satellites revolving at a rate of 12 hours per one turn on six orbits at an inclination angle of 55 degrees at approximately 20,200 Km above the earth. The navigation data required for position location is transmitted from three to four or more satellites, and is received by a receiver located on the earth so that a moving body having the receiver mounted thereon has calculated therefor position location data such as the position of the moving body, the moving speed thereof, etc. It is also possible to determine a velocity vector of the mobile body by measuring a Doppler frequency contained in a carrier wave. The transmission wave emitted by the GPS satellite involves two types, i.e., an L1 signal having a frequency of 1.57542 GHz and an L2 signal a frequency of 1.22760 GHz. Ordinary position location utilizes only L1. L1 is subjected to PSK modulation by a pseudo noise code (a synthetic wave of a C/A code used for satellite identification and navigation data such as satellite orbit information, time information, etc.) and spread spectrum, to be transmitted from the satellite. This radio wave is received by a GPS signal receiving apparatus as shown in FIG. 3. The 1.57542-GHz signal received by an antenna 300 is amplified by an L-passband amplifying circuit 301, converted by a down-converter section 302 to a first IF (intermediate frequency) signal of several tens of MHz to 200 MHz, and is further converted to a second IF signal of approximately 2 MHz to 5 MHz. The second IF signal is supplied to a voltage comparator 303 so that it is digitally-converted by a clock signal of several times the IF signal frequency by use of a voltage comparator 303. The output of this is spread spectrum data. In a message decoding circuit 304, the digital signal output by the voltage comparator 303 is subjected to spread spectrum by a C/A code that is the same pseudo noise code as that of the satellite generated by a C/A code generator 305, thereby obtaining navigation data. This operation is performed using a plurality of satellites. A position location calculating means 306 determines position location data from the navigation data of usually four satellites. As size reduction in GPS receivers such as that described above advances, consideration has been given to utilizing the GPS device for purposes of determining human running and walking moving distance or moving speed, such as disclosed in Japanese Unexamined Patent Publication (Kokai) No. H6-118156, etc.
Meanwhile, in order to measure the time period taken by a user to complete a particular segment of a running course (hereinafter referred to as a lap time), a required step must be taken in which a user, when passing a certain point, operates a button to record the lap time. Other means have been devised for this purpose, such as a transmitter being installed at a certain point to receive a signal to automatically record a lap time. Also, during running, physiological or "organic" data, such as the number of pulses or pulse rate, the number of steps or movements, etc., in addition to time data, is an important index representing performance. These types of organic indices are generally obtained by use of a button similar to that used in recording of a lap time.
Further, there is known a device, as disclosed by Japanese Unexamined Patent Publication No. H6-082576, for example, which is adapted to anticipate a time required for a user to move an arbitrary distance (broadly referred to herein as "motion amount") at an arbitrary speed (broadly referred to herein as "motion strength"). FIG. 4 is a structural view thereof, which has a pulse measuring means 400 for measuring a number of pulses when exercise is done at various a different motion strength. Thereupon, a calculating means 402 calculates a correlation between motion strength and the number of movement pulses. Then, if motion amount data input means 401 is supplied with motion amount data (distance data) to be run, the calculating means 402 calculates an expected motion strength (speed) and a completion time of a predetermined amount of motion (distance) based on the correlation between the motion strength and the number of movement pulses, and outputs the estimated values to an output means 403.
Where the conventional portable device is used in conjunction with an exercise such as running to measure a lap time or organic information, various manual operations are required when arriving at a destination point. Also, even the receiving of a signal from a transmitter previously installed to automatically memorize a certain point cannot provide advance information as to at which point it is located. Also, such a transmitter is not necessarily installed at a desired point. In particular, in physical training, it has been considered an important performance index to assess how the time information and organic information vary with respect to a specific distance.
Meanwhile, when calculating a predetermined motion amount (distance) and expected arrival time, it has been necessary to measure movement pulse data while performing a trial run at various different speeds to determine a correlation between the speed and the number of movement pulses.
Also, when determining an expected motion strength (speed) there is a necessity of using the coefficients based on a general consideration such as wearer's age and endurance criteria so that it is difficult to reflect an individual difference or physical conditions, etc.